A battery is largely classified into a primary battery and a secondary battery, wherein the primary battery produces electricity by a non-reversible reaction, which is non-reusable after the battery is used once, and includes a largely used dry battery, a mercury battery, a voltaic battery, and the like, as examples; meanwhile, the secondary battery uses a reversible reaction unlike the primary battery, which is reusable by charging after being used, and includes a lead storage battery, a lithium ion battery, a nickel-cadmium (Ni—Cd) battery, and the like.
In general, the secondary battery includes a plurality of unit cells therein, and has a form in which a pair of external terminal tabs connected to electrodes of each cell (that is, tabs provided with a pair of one cathode, in which cathodes of each unit cell are connected, and one anode, in which anodes of each cell are connected for one battery to function as electrodes) are exposed to the outside. In particular, as described in Korean Patent Laid-Open Publication No. 2007-0053614, a stack-type lithium ion battery has a structure in which a plurality of anodes and cathodes immersed in an electrolyte are stacked with separators interposed therebetween and electrically connected to each other in series or in parallel. In the secondary batteries as described above, it is general that a plurality of anodes and cathodes are connected to each other to form one pack battery, rather than using a single anode and a single cathode.
As described above, the stack-type secondary battery in which a plurality of anodes and cathodes are stacked with separators interposed therebetween has a limitation in that the entire battery should be discarded even in a case in which only one film among the plurality of films (anodes, cathodes, and separators) configuring the battery is damaged or deteriorated.